This is a second international conference, the first conference was held in May of 1997 in Ascona, Switzerland and attracted 70 scientists from all over the world. An indication of the success of the 1997 conference was exceptional quality of presentations, the length and extent of discussions and most of all the lively and animated evening discussions. During these discussions, which I vividly recall to date, controversial issues regarding peroxynitrite were critically discussed and evaluated. The resounding success of the first meeting and the overwhelming desire of all the participants to attend another conference resulted in the decision to put together a second meeting. The meeting is sponsored by the Nitric Oxide Society (see letters). We anticipate that the second meeting will bring together approximately 100 scientists; chemists, biochemists, biologists, physicians, neuroscientists and molecular biologists. The format will be similar to the first meeting and of Gordon conferences, with morning oral presentations followed by group discussions in the evening. The objectives will be to exchange information and engage in discussions regarding the chemistry, biology and medical applications of peroxynitrite. Peroxynitrite is the molecule formed by the reaction of nitric oxide and superoxide. A number of the chemical and biological functions of peroxynitrite have been described but almost monthly a new function or a possible role in human pathophysiology is reported. The number of laboratories contributing to investigations regarding peroxynitrite has grown over the years. A quick search in biomedical databases using peroxynitrite as the key word produced over 1,000 articles for the past eight years. However, the majority of the peer-reviewed articles (469) were published during the last two years following the Ascona meeting. Moreover, NIH currently funds a number of participants of the first meeting to work on peroxynitrite. Using the NIH search engine we found 86 projects that are currently funded by NIH to investigate the role of peroxynitrite in the pathogenic mechanism of neurodegenerative diseases, respiratory distress, cardiovascular disorders, cancer and a number of other disorders. Moreover, the most important advancements in this field are the recent evidence for the participation of peroxynitrite-mediated nitration of proteins in the pathogenesis of neurodegenerative diseases of aging.